Devices for imaging body cavities or passages in vivo are known in the art and include endoscopes and encapsulated cameras. Endoscopes are flexible or rigid tubes that pass into the body through an orifice or surgical opening, typically into the esophagus via the mouth or into the colon via the rectum. An image is formed at the distal end using a lens and transmitted to the proximal end, outside the body, either by a lens-relay system or by a coherent fiber-optic bundle. A conceptually similar instrument might record an image electronically at the distal end, for example using a CCD or CMOS array, and transfer the image data as an electrical signal to the proximal end through a cable. Endoscopes allow a physician control over the field of view and are well-accepted diagnostic tools. However, they do have a number of limitations, present risks to the patient, are invasive and uncomfortable for the patient, and their cost restricts their application as routine health-screening tools.
Because of the difficulty traversing a convoluted passage, endoscopes cannot reach the majority of the small intestine and special techniques and precautions, that add cost, are required to reach the entirety of the colon. Endoscopic risks include the possible perforation of the bodily organs traversed and complications arising from anesthesia. Moreover, a trade-off must be made between patient pain during the procedure and the health risks and post-procedural down time associated with anesthesia. Endoscopies are necessarily inpatient services that involve a significant amount of time from clinicians and thus are costly.
An alternative in vivo image sensor that addresses many of these problems is capsule endoscope. A camera is housed in a swallowable capsule, along with a radio transmitter for transmitting data, primarily comprising images recorded by the digital camera, to a base-station receiver or transceiver and data recorder outside the body. The capsule may also include a radio receiver for receiving instructions or other data from a base-station transmitter. Instead of radio-frequency transmission, lower-frequency electromagnetic signals may be used. Power may be supplied inductively from an external inductor to an internal inductor within the capsule or from a battery within the capsule.
A capsule camera system with on-board data storage was disclosed in the U.S. patent application Ser. No. 11/533,304, entitled “In Vivo Autonomous Camera with On-Board Data Storage or Digital Wireless Transmission in Regulatory Approved Band,” filed on Sep. 19, 2006. This application describes a capsule system using on-board storage such as semiconductor nonvolatile archival memory to store captured images. After the capsule passes from the body, it is retrieved. Capsule housing is opened and the images stored are transferred to a computer workstation for storage and analysis.
The above mentioned capsule cameras use forward looking view where the camera looks toward the longitude direction from one end of the capsule camera. It is well known that there are sacculations that are difficult to see from a capsule that only sees in a forward looking orientation. For example, ridges exist on the walls of the small and large intestine and also other organs. These ridges extend somewhat perpendicular to the walls of the organ and are difficult to see behind. A side or reverse angle is required in order to view the tissue surface properly. Conventional devices are not able to see such surfaces, since their FOV is substantially forward looking. It is important for a physician to see all areas of these organs, as polyps or other irregularities need to be thoroughly observed for an accurate diagnosis. Since conventional capsules are unable to see the hidden areas around the ridges, irregularities may be missed, and critical diagnoses of serious medical conditions may be flawed.
A camera configured to capture a panoramic image of an environment surrounding the camera is disclosed in U.S. patent application Ser. No. 11/642,275, entitled “In vivo sensor with panoramic camera” and filed on Dec. 19, 2006. The panoramic camera is configured with a longitudinal field of view (FOV) defined by a range of view angles relative to a longitudinal axis of the capsule and a latitudinal field of view defined by a panoramic range of azimuth angles about the longitudinal axis such that the camera can capture a panoramic image covering substantially a 360 degree latitudinal FOV.
For capsule systems, with either digital wireless transmission or on-board storage, the captured images will be played back for analysis and examination. During playback, the diagnostician wishes to find polyps or other points of interest as quickly and efficiently as possible. The playback can be at a controllable frame rate and may be increased to reduce viewing time. A main purpose for the diagnostician to view the video is to identify polyps or other points of interest. In other words, the diagnostician is performing a visual cognitive task on the images. Therefore, it is desirable to have a video display system which will make the diagnostic viewing easy for identifying potential anomalies and increase the rate of detection. Sometimes there are dark areas in the captured images which make it hard to identify features within the dark areas. The capsule endoscope does not insufflate the gastrointestinal tract sufficiently as standard colonoscopy or virtual colonoscopy, which may cause portions of the gastrointestinal tract to become folded. The wall of the folded tract may not receive adequate lighting and consequently renders itself as dark areas in the captured image. Inside each of these dark areas, the real mucosa surface area is much larger than it appears in the captured image due to its perspective view. Therefore, the dark areas represent a substantial percentage of the GI tract mucosa area, especially for colon, where polyps or other pre-cancerous or even cancerous pathologies could exist and need to be detected. While a conventional endoscope may be less susceptible to the issue of folded lumen walls, the situation may still occur and causes dark areas in the captured images. It is desirable to use image processing techniques to enhance the image quality of the dark areas of captured images to help improve the visibility of features in the dark areas and improve the detection rate consequently. Furthermore, the developed technology should have no impact or minimum impact on the quality of non-dark areas. In addition, it may offer the diagnostician a further advantage by providing interactive control related to intensity stretch of the dark areas.